If you are having some strange performance issues on SQL Server, I usually like to see how the Hard Drive is performing. Microsoft released a great tool called SQLIOStress.exe. However this has now been superseeded with SQLIOSim.exe. You can download either the x86 or x64bit version from Microsoft.
Bascially all it does is attack the Hard Drive in similar scenarios as SQL Server would. So to run:-
Load SQLIOSim.exe and remove all drives apart from
the ones where you will have the SQL Database files save e.g. this is the default when I run on my server:-
So just select the files and click remove to get something like:-
Then click the top right hand icon to start the test:-
There are plenty of documents on the internet to interpret the result and what they mean. But I would also recommend downloading the SQLIOSimParser (just search in
codeplex) as this converts the results file into a simple to read csv file (just open it in Excel).